1. Field of the Invention
The present invention relates generally to an apparatus and method for multiplexing multiple end-to-end transmission links in a communication system, and in particular, to an apparatus and method for multiplexing multiple transmission links between a base station controller and a base transceiver system in a mobile communication system.
2. Description of the Related Art
In general, a mobile communication system includes a base station controller (BSC), a base transceiver system (BTS) and a mobile terminal. For communication, the base station controller is connected by wire to a mobile switching center (MSC) and the base transceiver system is wirelessly connected to the mobile terminal. Such a mobile communication system has typically provided a mobile subscriber with a voice service only. Recently, however, the mobile communication system tends to support not only the voice servile but also a high-speed data service.
Conventionally, a connection between the base station controller and the base transceiver system is uniquely independently made for each user. Further, a single link is set up between the base station controller and the base transceiver system, and the link is shared by a plurality of users. Meanwhile, the base station controller exchanges RLP (Radio Link Protocol) frames with the base transceiver system through a proprietary flow-control process, which is not a standard scheme and is unique for each manufacturer. In addition, the base station controller and the base transceiver system include a plurality of buffers in order to control priorities of packets exchanged between them during the flow-control process. An actual data exchange is made by a transport layer of a lower layer.
For the packet exchange, an ATM (Asynchronous Transfer Mode) scheme and an IP (Internet Protocol) can be used. The current mobile communication system typically uses the ATM scheme, a kind of an end-to-end connection scheme in which a physical link is associated with a virtual circuit (VC) on a one-to-one basis.
Describing a transmission procedure by a transmitter in the case where the physical link is associated with the virtual circuit on a one-to-one basis, in a transmission mode, a packet is transmitted through a transmission link established for its service. A receiver then receives the packet through the transmission link established for the service and provides the received packet to an upper layer.
Of the conventional mobile communication standards, the cdmaOne standard supports a service of 9.6/1.4 Kbps or 64 Kbps while the CDMA2000 1X standard supports a service of 153.6 Kbps, in a radio environment. In general, the base station controller communicates with the base transceiver system through an E1/T1 link. In this case, there is no difficulty in supporting the above low (9.6 kbps/14.4 kbps) and medium (153.6 kbps) data rate services because the E1/T1 link supports a rate of 2 Mbps and 1.5 Mbps. However, a mobile communication system proposed for high-speed data transmission (e.g., CDMA2000 1xEV-DO) provides a service of a maximum of 2.4 Mbps in the radio environment. That is, the future mobile communication system shall provide a rate higher than that of the E1 or T1 link in the radio environment. However, the conventional mobile communication system cannot support the high-speed data service, since the base station controller and the base transceiver system support a single connection link for each service, as stated above.